-LRB- CNN -RRB- -- Peru 's president arrived Tuesday night at a mine in southern Peru , where he was expected to lead an operation to reach nine trapped miners .

`` We have been able to talk with the miners . Their spirits are quite high , '' President Ollanta Humala told reporters outside the mine .

But more work needs to be done before the rescue begins , Humala said . Engineers were working to make sure the mine was secure `` so there are no victims , '' he said .

`` Those same engineers tell us that we have to wait a few hours . They have n't said how many , '' the president said .

The miners have been stuck since Thursday in the wildcat Cabeza de Negro mine in southern Peru .

Earlier Tuesday , one of the mining engineers in charge of the rescue declined to give a specific time frame for the operation .

`` We ca n't say how long it will take right now to get them out , but I can guarantee that they are alive , that they are in good health , and that ultimately they are going to be freed alive , '' engineer Carlos Bejarano said .

A cave-in over the weekend complicated efforts .

`` It 's very complicated work . We 're taking into account all the necessary security measures to avoid risks among the rescuers themselves , '' said Cesar Chonate , a regional head of Peru 's civil defense agency , the state-run Andina news agency reported .

Video from state-run TV Peru showed workers , wearing hard hats and headlamps , loading rocks into a pushcart by hand .

It was not clear what caused the initial collapse .

The miners have been getting oxygen , food and water through a tube , which has also allowed them to stay in contact with people above ground , Andina reported .

Peruvian Mining Minister Jorge Merino was also in the area and appealed to mining companies for their expertise , according to a statement from his office .

Mining is big business in Peru , which is a major world producer of copper , silver , gold and other minerals .

`` The important thing is that the nine people are alive . We wo n't abandon them , '' Merino said .

The ordeal stirred memories of a 2010 Chilean mine collapse in which 33 men were trapped underground for 69 days . All those miners were rescued , pulled one by one from hundreds of meters beneath the Earth 's surface with a specially designed capsule .

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NEW : Peru 's president says it will be `` a few hours '' before the rescue begins

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NEW : The miners ' `` spirits are quite high , '' President Ollanta Humala says

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Nine miners have been trapped since Thursday

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In 2010 , 33 miners were rescued after being trapped underground for 69 days in Chile